APCTP SEMINAR (Online & On-site)
• Title: Graphene-based Josephson junction microwave bolometer
• Speaker: Prof. Gil-Ho Lee (POSTECH, APCTP)
• Host: Prof. Yunkyu Bang (APCTP, POSTECH)
• Date & Time: Dec. 16 (Wed.) / 16:00 (KST)
• Venue: #512, APCTP HQ & Online via ZOOM
• ZOOM Link: https://zoom.us/meeting/register/tJEkceGvrzsiEtXg1wia86TrvXdgMpBazAjN
Sensitive microwave detectors are critical instruments in radioastronomy, dark matter axion searches, and superconducting quantum information science. The conventional strategy towards higher-sensitivity bolometry is to nanofabricate an ever-smaller device to augment the thermal response. However, this direction is increasingly more difficult to obtain efficient photon coupling and maintain the material properties in a device with a large surface-to- volume ratio. Here we advance this concept to an ultimately thin bolometric sensor based on monolayer graphene. To utilize its minute electronic specific heat and thermal conductivity, we develop a superconductor-graphene-superconductor (SGS) Josephson junction bolometer embedded in a microwave resonator of resonance frequency 7.9 GHz with over 99% coupling efficiency. From the dependence of the Josephson switching current on the operating temperature, charge density, input power, and frequency, we demonstrate a noise equivalent power (NEP) of 7×10-19 W/Hz1/2 , corresponding to an energy resolution of one single-photon at 32 GHz and reaching the fundamental limit imposed by the intrinsic thermal fluctuation at 0.19 K.